The data requiring to be transmitted is frequently assigned different service or priority classes so that correct data transmitting—for example within a pre-specified realtime constraint—can be insured. In such a scheme low priority data will then be transmitted over a transmission link only if there is no higher priority data to be transmitted. The consequence thereof in some cases is that low priority data will block a link for a certain period of time because the higher priority data was not yet available for transmission at the time the decision was made about sending the lower priority data.
Particularly in the case of links having a low data transmission rate, for example ISDN (Integrated Services Digital Network) payload data channels or slow uplinks of ADSL (Asymmetrical Digital Subscriber Line) connections, this situation results in unacceptable delays for the higher priority data.